Within a residential human laboratory procedures will be studied for reducing methadone self-administration by volunteer methadone patients. The methods of experimental human drug self-administration will be used to study environmental behavioral pharmacological factors which influence oral methadone self-administration and which can be arranged to assist or facilitate patients' self-regulated detoxification from methadone. Participants will be volunteer methadone maintenance patients seeking to detoxify from methadone. Total daily doses will be available in multiple (10-30) small "unit" doses. Patients may self-regulate the number of units received daily. We will examine the effect upon methadone self-administration of variations in 1) response requirement to obtain unit doses; 2) the potency of the unit dose; and 3) the scheduled consequences of ingesting each unit. On the basis of these studies we will develop a contingency-assisted detoxification procedure which will be compared in terms of drug-intake pattern and success to an unassisted self-regulated detoxification procedure. Finally, following detoxification limited amounts of methadone will remain available for self-administration in studies which seek to identify factors which influence the likelihood of post-detoxification self-medication (relapse).